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51316-7322-Methodology for the comparative evaluation of batch biocide performance against microbial corrosion

This study describes a laboratory test system which was specifically developed to assess the ability of biocides to lower microbial corrosion rates. It was found that the common oilfield biocides THPS and glutaraldehyde, dosed at concentrations of 300 ppm for 4 hours weekly over 5 weeks, could reduce MIC rates from 109.7 mpy to as low as 4.3 mpy

Product Number: 51316-7322-SG
ISBN: 7322 2016 CP
Author: Dennis Enning
Publication Date: 2016
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Microbiologically Influenced Corrosion (MIC) is one of the main material degradation mechanisms in oil and gas operations. One typical component of offshore oil and gas producing facilities are seawater injection (SWI) systems, which maintain or restore reservoir pressure through injection of deaerated seawater into the reservoir (for secondary oil recovery). The associated carbon steel piping and pipelines are prone to the development of anaerobic biofilms which, unless adequately controlled with biocides, lead to corrosion and ultimately to costly repairs or even pipeline replacements. Common techniques for biocide qualification focus on the assessment of how effectively biocides ‘kill’ microorganisms. However, such testing cannot adequately answer the question of whether a particular biocide treatment regime can be expected to protect SWI systems against microbial corrosion. This study describes a laboratory test system which was specifically developed to assess the ability of biocides to lower microbial corrosion rates. The developed methodology is based on the ability to create extremely high microbial corrosion rates in the laboratory. It was found that the common oilfield biocides THPS and glutaraldehyde, when dosed at active concentrations of 300 ppm for 4 hours weekly over 5 weeks, could reduce MIC rates from 109.7 ± 13.3 mpy (2.86 ± 0.34 mm/yr) to values as low as 4.3 ± 1.3 mpy (0.11 ± 0.03 mm/yr). Both biocides performed better on clean steel surfaces than on surfaces with already pre-established biofilm, highlighting the importance of mechanical pipeline cleaning (pigging) in addition to chemical treatment. THPS appeared to deliver more reliable chemical control of MIC under the tested conditions which were characterized by direct, SRB-driven corrosion in (artificial) anoxic seawater.

Key words: downloadable, MIC, sulfate-reducing bacteria (SRB), microbial corrosion rate, biocide testing, seawater injection system

Microbiologically Influenced Corrosion (MIC) is one of the main material degradation mechanisms in oil and gas operations. One typical component of offshore oil and gas producing facilities are seawater injection (SWI) systems, which maintain or restore reservoir pressure through injection of deaerated seawater into the reservoir (for secondary oil recovery). The associated carbon steel piping and pipelines are prone to the development of anaerobic biofilms which, unless adequately controlled with biocides, lead to corrosion and ultimately to costly repairs or even pipeline replacements. Common techniques for biocide qualification focus on the assessment of how effectively biocides ‘kill’ microorganisms. However, such testing cannot adequately answer the question of whether a particular biocide treatment regime can be expected to protect SWI systems against microbial corrosion. This study describes a laboratory test system which was specifically developed to assess the ability of biocides to lower microbial corrosion rates. The developed methodology is based on the ability to create extremely high microbial corrosion rates in the laboratory. It was found that the common oilfield biocides THPS and glutaraldehyde, when dosed at active concentrations of 300 ppm for 4 hours weekly over 5 weeks, could reduce MIC rates from 109.7 ± 13.3 mpy (2.86 ± 0.34 mm/yr) to values as low as 4.3 ± 1.3 mpy (0.11 ± 0.03 mm/yr). Both biocides performed better on clean steel surfaces than on surfaces with already pre-established biofilm, highlighting the importance of mechanical pipeline cleaning (pigging) in addition to chemical treatment. THPS appeared to deliver more reliable chemical control of MIC under the tested conditions which were characterized by direct, SRB-driven corrosion in (artificial) anoxic seawater.

Key words: downloadable, MIC, sulfate-reducing bacteria (SRB), microbial corrosion rate, biocide testing, seawater injection system

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